It is well known in the art to provide a vacuum cleaner that comprises a nozzle assembly for picking up dirt and debris from the surface to be cleaned such as a carpeted or hardwood floor and a canister body that has a dust bag for collecting dirt and debris and a suction motor and fan assembly for generating the necessary negative pressure to draw the dirt and debris into the dust bag for collection. The canister body is, of course, supported on wheels so that it may be easily moved from room to room during cleaning. Many vacuum cleaners also include a separate drive motor for driving a rotating agitator brush which includes bristles, beater bars or other structure for beating dirt and debris from the nap of a carpet so that it can be drawn by negative pressure through the nozzle to the dust bag for collection.
As with any electrical appliance, fluctuations in line voltage including line surges such as are caused by lightning strikes, line equipment malfunctions or other reasons affect the electrical supply voltage and, therefore, the current supplied to electrical components including e.g., the switches and the motor or motors of the vacuum cleaner. Additionally, it is well known that air with entrained dirt and debris moving at high speeds through the nozzle and/or wand of the vacuum cleaner and the body of the canister into the dust bag often produce a build-up of electrostatic charge in those components. In extreme situations, the accumulated electrostatic charge may reach an electrical potential sufficiently high to cause an electrostatic discharge which could result in an unpleasant shock to the user of the vacuum cleaner and/or damage to the electrical controls or possibly even one or more of the motors of the vacuum cleaner.
In order to guard against such problems the assignee of the present invention has previously equipped the power control circuit of a vacuum cleaner with a reset toggle which shuts the power control circuit and, more particularly, the microprocessor controller of that circuit off in the event of overwhelming noise in the form of power supply and/or static discharge spikes. In past designs the reset toggle has incorporated a relatively small 0.01 .mu.F capacitor between the microprocessor controller and the reset toggle and a second 0.01 .mu.F capacitor between the reset toggle and ground. The capacitors are generally sized so that the reset toggle only operates when noise from power supply and/or static discharge spikes is at least of a certain, predetermined minimum level.
While generally useful for its intended purpose, the prior art design in question is somewhat limited in its ability to limit the operation of the reset toggle: that is, to prevent undesired resets of the power control circuit and interruption of power to the motor or motors of the vacuum cleaner in response to power supply and static discharge spikes that are insufficient to cause true damage or improper operation of the electronic components of the vacuum cleaner. Accordingly, a need is identified for an improved power control circuit for providing full and complete protection of all the electronic components of the vacuum cleaner from potentially damaging power supply and static discharge spikes while also avoiding undesired interruption to the operation of the vacuum cleaner in response to otherwise insignificant power supply and static discharge spikes.